Technical Field
The present disclosure relates generally to high affinity or enhanced affinity T cell receptors (TCRs) specific for antigens associated with a hyperproliferative disease. More specifically, the present disclosure relates to TCRs with high or enhanced affinity against a human Wilms tumor protein 1 (WT-1) epitope, T cells expressing such WT-1-specific TCRs, nucleic acids encoding the same, and compositions for use in treating diseases or disorders in which cells overexpress WT-1, such as in cancer.
Description of the Related Art
T cell receptor (TCR) gene therapy is an emerging treatment approach designed to overcome obstacles associated with conventional T cell adoptive immunotherapy, such as the extensive time and labor required to isolate, characterize, and expand tumor antigen-specific T cells (Schmitt et al., Hum. Gene Ther. 20:1240, 2009). Another hurdle is that most identified tumor antigens that can be targeted by conventional T cell immunotherapy are over-expressed self-proteins, so high affinity T cells specific for these antigens are generally eliminated during thymic selection, and are rare or non-existent in the peripheral repertoire.
Strategies are being developed to enhance the affinity of TCRs intended for use in TCR gene therapy (Udyavar et al., J. Immunol. 182:4439, 2009; Zhao et al., J. Immunol. 179:5845, 2007; Richman and Kranz, Biomol. Eng. 24:361, 2007). These approaches generally entail generating libraries of mutated TCR genes and subsequent screening for mutations that confer higher affinity for the complex of target peptide with major histocompatibility complex (MHC) ligand. Mutations are usually targeted to the complementarity determining regions (CDRs) known to interact with the peptide (CDR3) and/or MHC (CDR1/2) (Wucherpfennig et al., Cold Spring Harb. Perspect. Biol. 2:a005140, 2010). But, changes to MHC contact residues may create a risk in the clinical setting since this can increase the affinity for MHC independent of peptide or increase the likelihood of cross-reactivity (off-target effects). This notion has been highlighted by the results of a trial, in which T cells expressing a TCR containing CDR2 mutations were infused into patients and mediated rapid and fatal toxicity from unpredicted cross-reactivity with a disparate self-antigen expressed in the heart (Cameron et al., Sci. Transl. Med. 5:197ra103, 2013; Linette et al., Blood 122:863, 2013). Certain available methodologies used to target specific CDR residues for amino acid substitution limit the diversity of the generated libraries, as these are generally constrained by the length of the parental CDR sequence. In contrast, the natural process generally produces greater diversity in the thymus, where the V(D)J recombination machinery active during T cell development results in TCR gene rearrangements that generate highly diverse CDRs, particularly CDR3s, that vary in both length and amino acid composition.
A strategy for targeted T-cell therapy achieving a maximal clinical effect that would be accompanied by minimal immunological toxicity involves identifying disease associated antigens with high expression in and presentation by, for example, a malignant cell compartment, but without significant expression in normal tissue. For example, several acute myeloid leukemia (AML) associated antigens have been described, and Wilms tumor protein 1 (WT-1) has been shown to be expressed in the leukemia stem cell (LSC) compartment of the majority of AML patients at levels significantly higher than in physiological hematopoietic stem cells (HSCs). WT-1 is being targeted in clinical trials both with adoptive T-cell transfer and peptide vaccination (see, e.g., U.S. Pat. Nos. 7,342,092; 7,608,685; 7,622,119). In addition, WT-1 expression has been reported to be a marker of minimal residual disease because increased transcript levels in patients with AML in morphologic remission were predictive of overt clinical relapse (Inoue et al., Blood 84:3071, 1994; Ogawa et al., Blood 101:1698, 2003).
Since WT-1 is an intracellular (usually nuclear) protein, immunotherapies targeting WT-1 generally use cellular approaches aimed at generating WT-1-specific CD8+ cytotoxic T lymphocyte (CTL) responses that recognize peptides presented on the cell surface by MHC class I molecules. For induction of a CTL response, intracellular proteins are usually degraded by the proteasome or endo/lysosomes, with the resulting peptide fragments binding to MHC class I or class II molecules. These peptide-MHC complexes are displayed on the cell surface where they are bound by T cells via the peptide-MHC-TCR interaction. Peptides derived from the WT-1 protein can be used in a vaccine in humans to induce human leukocyte antigen (HLA)-restricted cytotoxic CD8+ T cells that are capable of killing tumor cells. However, because WT-1 is a self-protein, such immunization may only elicit responses by T cells with low affinity TCRs. In addition, antibodies against WT-1 are detectable in patients with hematopoietic malignancies and solid tumors, which show that WT-1 can be a highly immunogenic antigen (Gaiger et al., Clin. Cancer Res. 7 (Suppl. 3):761, 2001).
Clearly there is a need for alternative TCR gene therapies for use as highly specific, WT-1 targeted immunotherapies directed against various cancers, such as leukemia and tumors. Presently disclosed embodiments address this need and provide other related advantages.